Traffic control system



Feb. 13, 1945. c. c. MaCALLISTER TRAFFIC CONTROL SYSTEM Filed Aug. 6, 1942 IQIZQQLQQ Copeland C. MacAllisber Hi5 Attornegn Patented Feb. 13, 1945 TRAFFIC CONTROL SYSTEM Copeland .C. MacAllister, Winchester, Mass., as-

signor to General Electric Company, a corporation of New York Application August 6, 1942, Serial No. 453,813

1 Claim. (01. 177-337) My invention relates to trafllc signal systems and more particularly to systems wherein a group of intersection controllers are each brought into and maintained in synchronous operation with a master controller.

One object of my invention is to provide improved apparatus for controlling the intersection controllers during periods of resynchronization.

For a better understanding Of my invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claim.

The accompanying drawing illustrates diagrammatically a traflic control system embodying my invention.

Referring to the drawing in detail, a master controller I0, illustrated merely by a rectangle of dotted lines, includes a switch II operated by a cam I2 and controls a group of intersection controllers through a circuit including any one of a group of conductors I3, I4 and I5 selected by a selector switch I6.

Only one of the intersection controllers controlled through this group of conductors is illustrated diagrammatically. It is preferably of the type fully described in United States Letters Patent 2,236,299, issued to Reid, March 25, 1941. This controller operates groups of trafllc signals I1 and I1 connected by a cable I8 to a switching mechanism I9 indicated merely by a rectangle. This switching mechanism may be of any suitable type operable step by step in response to current impulses to energize a predetermined combination of signal lamps at each step. Each combination of signals is held for a predetermined time period which constitutes a signal period.

The timing mechanism, also a part of the controller, for determining the length of the time period between the step-by-step actuations of the switch mechanism I9 is driven by a motor provided with an operating field 2|, 9. braking field 22, a driving shaft 23 and a driving pinion 24. The pinion 24 is in driving engagement with a gear 25 mounted upon a dial shaft 26 to which is attached a dial 21. The dial, which may be termed a timing dial, is provided with two concentric rows of radial slots 28 and 29. The outer row of slots 28 carries a group of keys 30 to 85, inclusive, and the inner row of slots 29 carries a group of keys 31 to 39, inclusive. The keys are spaced from each other by being positioned in selected slots,

of which 100 are available in each row, to actuate switch contacts placed in the path of movement of these keys. In the illustrated controller, five resilient switch arms 40 to 44, inclusive, are mounted parallel to each other upon a single suitable block 45 and the arms are provided with actuating blocks attached to the forward ends of the switch arms. Contact arm 40, nearest to the dial, is provided with an actuating block 46 the end of which extends into-the path of movement of and is raised by each of the keys 3I, 32, 33, 34 and 35 as they are moved past the block. At each instance a contact 41 carried by the contact arm is raised into engagement with a stationary contact 48, thereby momentarily completing a circuit through a conductor 49 to the switching mechanism IS. The contact arm is connected by a conductor 50 to the switching mechanism I9 and the completion of this circuit sends a current impulse through the circuit which effects an actuation of the-switching mechanism to change to a succeeding combination and period of the signals I1 and I1. v p

The second contact arm M is provided with an actuating block 5| and is operated by the key 30 only, this key being provided with a notch to avoid actuating block 46. This actuation occurs once during each revolution of the dial 21, thereby closing a circuit at contact 52 on the arm M, and a stationary contact 53. The stationary contact 53 is connected to the switching mechanism I9 by a, conductor 54 and the contact arm 4| is connected to the switching mechanism by a conductor 54. In a single rotation of the dial 21, which is a complete cycle of operation for the dial, the contacts 41, 48 are operated to effect at each actuationan operation of the switching mechanism I9, and the contacts 52, 53 are operated by the key 30 to complete a cycle of operations. The key 30 and the circuit closed thereby are provided for operating the switching mechanism at one selected position of the dial. The switching mechanism is arranged so it will move up to a corresponding position in its cycle of operation and will move past that position only when key 30 actuates its contacts, thereby to maintain ,a predetermined relationship between the cycle of operation of the dial and the similar cycle of operation of the switching mechanism. The switching mechanism I9 may be any suitable program switching mechanism but is preferably of the rotating drum type actuated by a' a troller is provided. with one or more circuits and.

with the necessary'switches to energize-the'brak ing field 22 of the dial motor 20 whenever the controller is out of its proper operating relations" ship. In the illustrated example three contact arms 42, 43, 44 are provided in each'secondarycontroller, each being provided with asuitable.

actuating block, which are operated respectively by the dial keys 31, 38 and 39, the key 31 operating the arm 42, the key 38 operating the arm 43 and the key 39 operating the arm 44; The con tact arms are respectively connected to the com.-.-

mon conductors I3, l4 and I through conductors 55; 56- and 51, other"controllers being connected to the samecommon conductors by conductors- 55', 56', 51 and;55f;', .565, 51-.. Thenth'ree'cona ductors and. three contact mechanisms. are. pro:- vided. so as to make itpossibleztozoperate the'secs ondary controller. in the three distinctirelatione ships-with the; master. controller which-are de1-vterminedby the positioningof the;respective:keys in the-innerrow of slots..29'.- Only one ioftheacon (motors-13,. l41and;.|5-isefiective atsany one time tovcarryj current. to the;.-'fie1d:'22, being. :selected;

by: the. selector. switch. l6.= If switch l6'is set as; illustrated in the drawing, a'circuit is established:

to the. common conductor.

operated contacts to a-conductor wand-through. field22 to ground whenever l5, conductor" 5 through contactrarmi44; through its respectively;

der andraises the actuating. block of thecontact arm 44. The circuitto the. selector switch: I tend to the common conductor passes through. the. master controller andisarrangedto be broken.

by the, master controller switch .I I once-during each. operating. cycle.

When. the. current inithe.

field 22 is so interrupted, the dial in eachstopped secondary controller moves its key to break the circuit at. the. respective contacts. and. thereby is.

free .to operate for. acomplete.revolutionflof the.

dial-.before the. key again..closes theibraking or resynchronizing, contactsto .stop the dial.

In accordance. with my. invention. the master switch] I is not connected. directly to theselector sWitchlB but .is' connected through an intermediate auxiliary timing apparatus which may be.

assembled in the casingof the .mastercontroller or may be assembled. in a separate casing indi cated generallyby the dott'edlrecta nglei.59'. This apparatus. includes a timingdial 60, similar tothe timing diali2'l, driven by'a motor. 61 provided" with a driving field Bland a 'braking'field fiiit'" The timing dial is provided withpne' or -more groups of keys such as-64;' 65 and 66,also61-; 68

and 69. The keys-operate contact arms-103 TI" and 12, respectively. Thecontact armlfl is pro vided with a pair 'ofnormally "opencontacts 13;:-

normally open-contacts", 1B, and'the contact arm--12 is provided with -a =pair=of normally closect contacts IT, 18. a

This auxiliary "timer also includesa relaypcomiprising an operating. coil 8larrange'dltorzactuateta a normally closed contact, and .a switchrcomew prising .an operating-coil. v93.arranged-to. actuatecontactsrlll, 9|and.:95 or which.,87'-and. 9l *are. normally open 2111112195 =isgnormally closed-. The-1 circuits;;.controlled::by ther energization andi de. 755;

energization of these coils through their respective contacts will be traced in the description of the operation of the system.

The master sWitch ll normally establishes a circuit from a source of current indicated by a plus sign through a conductor 80, relay coil 8|, conductor 82, conductor 83, through the normally closed contacts 11, I8, contactarm 12. and conddctor 84 t'othe'selector'switch IS. The circuit thu traced places potential upon the common conductor I 5 and whenever the contact arm 44 of a secondary controller is actuated current flows to the braking field 22 to stop immediately the motorand the timing dial, thereby retaining the 1,contact .arm inth'econtact closing position. This position i Lretainedz-by the secondary controller dial until the braking field circuit is opened. This perlod is normally referred to as the resynchrothekey 39 moves .un

thereby? break the. braking coil circuit nizing. period and if the master switch alone were to control the circuit thi period could be of a lengtlr almost equal to the length'ora signaling cycle; Iftraffi'c were" correspondingly held" up on: a busy highway; considerable-congestion would ensue It is therefore desirable to limit theavail able synchronizing time in any one signa'l cycle to: a" short period and to distribute the total-required: resynchronizing time period in increments of this: total: time: period izr successive cycles of operations. It.is. therefo1'ethefuncti'on of the auxiliary timing device; operating through the dialJiO, to arrange: for: the release of-the secondary controllers within" ai predetermined l short time" periodcafter: theifirst secondary? controller of th'e system has been stopped.

The.dial:.:60; as shown in the drawing; is ina position at which the: key'x65xclos'es thecontacts 15 and 16. This establishes a circuit to the'brak ingifield B3 thereby:effecting-it stoppageatithis position The-circuit '-may;'-' be traced. from -the grounded end of: the: braking:- fieldir 631' through 4.; thesfield, through aconductor: 85, through: the: contacts 15,.16; contact arm ='ll,' conductorfBB; closedswitch contact 8'! tea source. of-icurrent in dicated by a plus sign. In the: position'illustrateds therefore; the dial "is stationary.

During .operation, if a secondary controller falls: out on. synchronism and 'currentxfiows through l themaster controller: switch-ll andthe auxiliary-i timing. device to the.:conductor; I5 through s'thes circuitca ctracemthe auxiliary timer relay coil! 8| is energized and opens its contacts 88to-break= a circuit from the source of current indicated by the..plussign at the relay contacts 88'; throughw conductor. 89;. conductor 90; c1osed.iswitch::contact-9|, conductor-92 to1the switchco-il 93 and." through the coil .to ground, therebydeenergizing i the switchcoil. 93.and effecting the openinng :ofwthe contacts 8'l.and- 9l--and.the closing 20f con"- tacts 95 controlled by this coil. The -closing of contacts 95-establishesashunt circuit around the'coil 8L Thiscircuitmay betracedrromrconductor 80-through conductor 98, contact 955 to.- conductor-"82. Thi is .a. low resistance path and deenergizescoil 8.! sufiicientlyto causeit to drop and therebyreclose the contact'88.-'

The. opening of. contact 87 by the deenergizationofi the coil 93.breaksvthe circuitito thebraking field-63 and allows the motor 6| to-drive the?- auxiliary timer dial-60 to move the key-.65 andr at the con? tactsJS, 16-; Within apredetermined period-de termined .by the speeds: of thevdialio and by; the positioning-ofhthesubsequent key, :69 in the diaL; the key. 69. is moved. into .position' -to liftthe. con tact-arm to: separate-:the contacts."l'l f'l8 andothereby break the circuit to the conductor IS. The efiect of this momentary breaking of the circuit is the same as the breaking of that same circuit by the master controller at switch I l and permits all of the secondary controllers which have been stopped by the energization of the conductor IE to resume operation. The dial 60 continues to move and within a short time its key 94, 92 to relay coil 93 and to ground, thereby ef fecting a reclosing of the switch contacts 9| and 81 and an opening of the contact 95.

The closing of switch contact 9| establishes a holding circuit for the coil 93 through conductor 89 and relay contacts 88. The closing of this contact 9| maintains the energization of coil 93 though the dial moves the key 61 past the actuating block for contact arm 10 and causes the contacts 14, 13 to separate. The closing of contact 8'! by the energization of coil 93 establishes a circuit from a source of current through the contact 81 and the conductor 86 to contact arm H. The opening of contact 95 opens the shunt circuit around the relay coil 8|.

The dial 80, with this arrangement of the switch and relay contacts within the auxiliary timer, continues to operate and moves key 68 into position to close the braking coil circuit for its driving motor 61 at the contacts 15, 16 as previously traced, the closing of contact 81 having placed potential on contact arm 1| through conductor 86. The dial 6|] then remains stationary until the next energization of the relay coil 8| by current flowing to one of the braking fields of the secondary controllers. The dial 60, together with its driving apparatus, relay 81 and the switch 93, may be enclosed within a single controller casing as indicated by dotted lines or may be built into the master controller ll. Its function, as above pointed out, is to deenergize the common or interconnecting conductor between the master controller and the secondary controllers at a, predetermined period of time after'the beginning of flow of current within that conductor. It is obvious that as soon as a single controller calls for braking current the timing apparatus begins to operate and interrupts that current within a predetermined time period after the inception of current flow. Any subsequently stopped secondary controller that may be connected to the common conductors, as indicated at 51', 56, 55' and 51", 56", 55", is restarted at the end of that predetermined period of time after the first controller i stopped, so that each of the secondary controllers is not necessarily stopped for the full period for which the auxiliary timing apparatus is set. The auxiliary timing apparatus merely provides for a limitation of the maximum time for which any secondary controller may be stopped during any one cycle. As a. result of this operation, the secondary controllers continue operation in out-of-synchronism relationship through successive cycles but with a successively diminished out-of-synchronism relationship. Such out-of-synchronism relationship may exist when the intersection controllers are first placed into operation and occurs whenever the selector switch I6 is operated to select a different common conductor through which a corresponding and predetermined oper ating relationship is selected.

What I claim as new and desire to secure by Letters Patent of the United States is:

In a trafiic signal system, a combination of a master controller operated at a predetermined signal cycle, a group of secondary controllers each including a timing mechanism and operating at a signal cycle length corresponding to the signal cycle length of said master controller, current operated means in each controller for stopping said controller at a predetermined instant in its operating cycle, a common circuit connecting said secondary controllers to said master controller,

means for interrupting said common circuit for restarting said econdary controllers at a predetermined instant in the master controller operating cycle, an auxiliary timer, means for starting said auxiliary timer at the instant current flows to any one of said secondary controllers in said common circuit, means operated by said auxiliary timer for interrupting said common circuit within a predetermined time period, and means for effecting operation of said auxiliary timer for a full preset operating period independently of current variations resulting from the variations in the number of controllers being stopped for resynchronization in said common circuit during the operating period.

COPELAND C. MACAILISTER. 

